Aortocoronary bypass for coronary atherosclerosis is a quantum step in surgery for coronary artery disease. The concept of the bypass and the demonstration that it is applicable to a high percentage of patients with arteriographically proven severe symptomatic coronary atherosclerosis is the essence of this advance, not the saphenous vein graft per se. Several other recent coronary operations were as enthusiastically lauded during the first two to three years following their introduction. Much of the mistaken enthusiasm for two procedures--the Vineberg implant, the endarterectomy and gusset procedure--was based on the demonstration of early angiographic patency alone without regard to quantity of flow or its effect on myocardial function. This project is designed to study early and late patency in a series of aortocoronary bypass grafts and to utilize the non-invasive technique of myocardial scanning and imaging to compare the reliability of these newer techniques with the invasive technique of coronary arteriography. These data will be correlated with measurement of myocardial function. This project is also designed to obtain objective evidence as to the significance and perhaps cause and prevention of interoperative myocardial infarctions during aortocoronary bypass surgery. Additionally, this study will focus on causes for bypass failure, specifically related to changes in the venous grafts such as intimal hyperplasia of the proximal anastamosis.